I recently bought a Jamis Nova 53cm cyclocross bike. I'll be using it mostly for commuting and frequently in wet weather (Portland, OR). BTW, I'm just over 5'10" and have about a 32" inseam. I bought this size as I've heard with cross bikes it's a good idea to go a little smaller.
When standing over it with my cycling shoes, I have about 1"-2" clearance from the top tube. I've been told this is about right. The issue is that I've also been told, when on the drops, that the hub should "disappear" behind the handlebar. Well, the hub is slightly ahead of the handlebar (if my elbows are bent). Otherwise, it feels comfy enough. Everything seems to be in the right place (legs, torso, etc), it's just that I'm afraid I might be a bit too far forward on it. I haven't done any long rides on it, though. Should I ride it for a while and make adjustments if it's too small? Other options (I can still return it)?
When I was working on the setup of my new bike, I was looking at the same issue. In the end, I adjusted the saddle so it felt comfortable (in terms of reach and leg position) and just started riding. I did look at a couple bikes that would have needed a different stem to fit me. At any rate, you should be able to get a good setup by manipulating the seat and the stem length. But the most important thing is your comfort - whatever feels best to you is the right setup. BTW, my bike is a Lemond Poprad and I have about 1" to 1.5" clearance on the top tube.
